1. Field of the Invention
The present invention relates to an ophthalmic apparatus, and more particularly to the ophthalmic apparatus suitable for measuring a refractive power of an eye to be examined, photographing the eye, or the like.
2. Description of Related Art
Conventionally, regarding a method of an alignment of an eye to be examined utilized in an ophthalmic apparatus, one widely known method is to detect or observe an image of a target projected onto a cornea of the eye to be examined, and thereby place a corneal center and the apparatus at positions having a predetermined positional relationship with respect to each other. Referring to an apparatus, for example an automatic eye refractive power measuring apparatus or the like, which projects a measurement luminous flux into the eye and detects a reflected luminous flux from a fundus of the eye with a photo-detector, it is required that the measurement luminous flux or the reflected luminous flux to pass the pupil being appropriate in size for measurement. Generally, positions of a corneal center and a pupil center of one eye approximately correspond to each other. There may be cases, however, where the deviation from each other is considerably big. In these cases, if an alignment is done with respect to the corneal center of the eye, the measurement luminous flux (the reflected luminous flux) is likely to eclipsed by an iris. Due to this eclipse, the measurement luminous flux may not be reflected, which is necessary to carry out the measurement, and measurement errors are easily to be caused.
In addition, a size of a pupil varies depending on brightness of a sight and individual variation. In the case of an eye having a pupil small in size, even if the amount of deviation between the corneal center and the pupil center is relatively small, a measurement based on an alignment with respect to the corneal center easily results in errors for the same reason mentioned above.